Duplex receptacle cover plate with plug retaining means



Oct. 25, 1966 A. I. APPLETON DUPLEX RECEPTACLE COVER PLATE WITH PLUG RETAINING MEANS 3 Sheets-Sheet 1 Filed April 21, 1965 N m OE L N P P A v NI Oct. 25, 1966 P -row 3,281,758

DUPLEX RECEPTACLE COVER PLATE WITH PLUG RETAINING MEANS Filed April 21, 1965 5 Sheets-Sheet 2 [NV ENTOR Ann-we. I. APPLETON INVENTQQ Amwwa LAPELETON 5 Sheets-Sheet 5 A. I. APPLETON mmm mwm DUPLEX RECEPTACLE COVER PLATE WITH PLUG RETAINING MEANS Oct. 25, 1966 Filed April 21, 1965 United States Patent 3,281,758 DUPLEX RECEPTACLE COVER PLATE WITH PLUG RETAINING MEANS Arthur I. Appleton, Northbrook, Ill. (1713 Wellington Ave., Chicago, 111.) Filed Apr. 21, 1965,5812 No. 449,723 6 Claims. (Cl. 33991) This application is a continuation-in-part of my copending application, Serial No. 394,992, filed September 8, 1964 now abandoned.

The present invention relates generally to electrical outlets and more particularly concerns a cover plate with plug retaining means for use with an electrical outlet box. The invention finds particular utility when embodied in a cover plate for an outlet box having one or more plugreceiving sockets.

There are many situations in which it is highly desirable to insure that the power line, or cord as it is sometimes called, for an electrical apparatus does not become unplugged from the electrical outlet which supplies the current for the apparatus. This is particularly true in hospitals, laboratories and in some industrial buildings or offices where the uninterrupted operation of an electrical device may be of extreme importance, indeed critical. Although one obvious solution to this problem is to simply remove the plug entirely and connect the power line of the apparatus permanently, or semi-permanently, to an electrical junction box in the supply circuit, this solution is undesirable in many instances where it is necessary or desirable to quickly and conveniently disconnect the apparatus so that it may be moved.

In the past, various systems and devices have been tried in an effort to insure that the power cord of an electrical apparatus does not come unplugged from the supply outlet. These prior devices have, however, usually entailed a cumbersome connection between the plug and receptacle which requires considerable time and effort, it not talent, to couple and uncouple. In addition, these prior devices have, for the most part, at least, been unattractive in appearance, difficult to keep clean, and often hazardous to employees due to the use of external projections for effecting the connection.

Accordingly, it is the primary aim of the present invention to provide an improved receptacle plug retaining device which selectively and expeditiously locks the plug in the outlet receptacle or frees the plug for removal.

It is a further object to incorporate and substantially entirely enclose the plug retaining means within the cover plate for the outlet receptacle, thereby making the outlet attractive and non-hazardous.

A more detailed object is to provide a plug retaining means of the above type wherein the plug is quickly and automatically locked in the receptacle upon its insertion into the receptacle. It is a related object to provide a cover plate with self-contained locking means for retaining a plug in an outlet receptacle which is completely compatable with standard outlet boxes and receptacles and also permits the insertion of non-locking plugs therein.

Another object is to provide such a cover plate and locking means with convenient means for indicating that the plug is not to be removed and to disable the locking means while it is in its locking position.

Other objects and advantages of the invention will become more readily apparent upon reading the following detailed description and upon reference to the drawings, in which:

FIGURE 1 is a top plan view of a novel receptacle cover plate and locking means exemplifying the present invention.

FIG. 2 is a bottom plan view of the cover plate and receptacle shown in FIG. 1.

FIG. 3 is a fragmentary side elevation, partly in section, illustrating one plug in the receptacle and another plug separated slightly from the receptacle.

FIG. 4 is a bottom plan view of a typical plug of the type illustrated in FIG. 3.

FIG. 5 is a bottom plan view, similar to FIG. 2 with the receptacle omitted to better illustrate the details of the locking mechanism.

FIGS. 6 and 7 are fragmentary partial sectional views illustrating a plug separated from the novel cover plate and locking means and a plug locked in the receptacle by the locking means, respectively.

FIG. 8 is a fragmentary side view, partially in section, illustrating a modified plug that may also be locked in the receptacle by the novel cover plate.

FIG. 9 is a top plan view of a modified receptacle cover plate and locking means illustrating another embodiment of the present invention.

FIG. 10 is a fragmentary side elevation, partly in section, illustrating one plug positioned in the receptacle cover plate shown in FIG. 9; and

FIG. 11 is a bottom plan view of the cover plate shown in FIG. 9.

While the invention will be described in connection with certain illustrative embodiments, it will be understood that I do not intend to limit the invention to those embodiments. On the contrary, I intend to cover all alternatives, modifications and equivalents included within the spirit and scope of the invention as defined by the ap-' pended claims.

Turning now to the drawings, there is shown in FIGS. 1-3 an electrical outlet, indicated generally at 10, with which the present invention is concerned. Such an outlet typically includes a receptacle box 11 which may be of conventional construction and, therefore, only a portion has been shown here. Sufiice it to say that the receptacle box 11 is ordinarily conveniently mounted in an opening in the wall or floor of a building with the open end of the box generally aligned with the surface of the wall or floor. In other instances, the box, though difiering in external appearance and other details which are not significant in terms of the present invention, may be mounted in exposed condition.

Within the box 11 there is provided a conventional duplex-type electrical outlet receptacle 12. Since the construction of the receptacle 12 is not of particular importance to the practice of the present invention, it has been illustrated, for the most part, in block form. Suffice it to say that the receptacle 12 is mounted in the outlet box 11 by means of screws 13 which pass through openings in mounting cars 14 at each end of the receptacle and are received in threaded holes in inwardly projecting ears 15 formed integrally at opposite ends of the box.

In the illustrated embodiment, the receptacle 12 has been shown with a pair of polarized sockets 20 of conventional design. Thus, each of these sockets 20 is adapted to receive a polarized plug 21 of the type shown in FIGS. 3 and 4 in the manner illustrated in FIGS. 3, 6 and 7. It will also be understood that the polarized plug and socket arrangement insures that the prongs on the plug can only be inserted when the plug is properly oriented. In this way, a proper electrical connection between the electrical supply afforded by the receptacle and the apparatus coupled through a cord 22 to the plug is always achieved. Nevertheless, the use of such a polarized plug and socket is not critical to the practice of the invention and, accordingly, unpolarized components can be used, if desired.

In accordance with the present invention, an improved cover plate 25 is provided for the outlet 10 which includes means for selectively locking the plug 21 in its complementary socket 20. In the illustrated embodiment, the

cover plate 25 is shown to be of the flush-mounting type. In other words, the cover is provided with an enlarged peripheral margin 26 which extends outwardly past the outlet box 11 and thereby completely conceals the outlet box and opening in which it is mounted. On the other hand, a cover plate for an exposed-type outlet box could also be provided, if desired, without departing from the present invention. The cover plate 25 is secured in place with a single screw 27 which is received in a threaded opening in the receptable body 12 in the usual manner.

As best seen in FIGS, 3, 6 and 7, the cover plate 25 is provided with a pair of apertures 28 adapted to complementary receive a raised face portion of the two sockets formed on the receptacle 12. In addition, the cover plate is formed to define a socket-like depression 29 adjacent each of the openings 28. Each of the depressions 29 is thus adapted to receive a plug 21 as shown in FIGS. 3 and 7.

In further keeping with the present invention, the means tor selectively locking the plug 21 in its complementary socket 20 includes a spring-biased locking lever 30 which is substantially entirely enclosed by the cover plate 25. In the illustrated embodiment, the locking lever 30 is substantially L-shaped and is pivoted about a pin 31 secured to the cover plate and projects inwardly therefrom. To maintain the locking lever 30 in its locking position a helical spring 32 is provided to bias one end 33 of the lever through an opening 34 for-med in the wall of the depression '29. The opposite end 35 of the locking lever projects outwardly through an opening 36 formed in the margin 26 of the cover plate. Movement of the lever 30 may be eifectuated by pressing inwardly the extending portion 35 and thereby causing the latching portion 33 to retreat from the socket 29.

In order to lock the plug 21 in its complementary socket 20, the plug is preferably formed with a casing 40 in which a pair of notches 41 are formed. In the embodiment illustrated in FIGS. 3, 6 and 7 the casing 40 of the plug -21 is provided with a necked-down portion 42 which is adapted to initially enter the socket 29. Thus, the necked-down portion 42 acts as a cam surface against the tapered latch portion 33 of the locking lever 30. Conversely, the opposed grooves 41 defined on the casing 40 are formed with a transverse shoulder portion 43 against which the latch portion 33 of the locking lever firmly seats. Accordingly, it will be apparent that the plug 21 may be insertedinto the complementary socket 20 and the latch portion 33 of the locking lever 30 will be cammed out of the socket 29 and then snapped into the recess 41 due to the operation of the spring 32. On the other hand, the plug 21 may not be withdrawn from its socket without first depressing the other end 35 of the locking lever to unseat the latching portion 33 from the shoulder 43 of the locking groove 41.

It is an additional \feature of the present invention that the outer, or operating end 35 of the locking lever 30 is formed with a small aperture 44 therein to provide a convenient means for securing the locking lever in its locked positon. As best seen in FIG. 3, the locking lever can be held in its locked position by simply inserting a wire 45 through the aperture 44. The wire 45, of course, restricts movement of the operating end 35 of the locking lever into the opening 36 formed in the cover plate 25. The-wire 45 may also be used to secure an appropriate label or tag 46 to the locking lever 30. Such a label might indicate that the plug 21 in that particular socket is not to be withdrawn, for example, during a test period or until specific authorization has been given.

Turning now to FIG. 8, there is shown a modified embodiment of a plug 21a which is also adapted to be locked into its socket 20a. *In this instance, the plug 21a is formed with a machined body portion 50 with a pair of radially extending grooves 51 (only one of which is shown) adjacent the inner end of the plug 21a. It will be understood by those familiar with this art that plugs of the type shown in FIG. 8 may also be adapted to be received in an explosion-proof receptacle and that the grooves 51 are typically provided in conjunction with such a receptacle. With respect to the present invention, however, the grooves 51 serve the same purpose on the plug 21a as do the grooves 41 on the plug 21 shown in FIGS. 3, 6 and 7. In other words, the novel cover plate 25 with its enclosed locking means 30 is adapted to receive either a conventional type metal cased plug 21 in which appropriate grooves 41 have been formed or the more specialized explosion-proof plu-g 21a of the type shown in FIG. 8. Moreover, it will be understood that conventional plugs of the non-locking type can also be inserted in the sockets 20 of the outlet, if desired A further modification of the present invention is shown in FIGS. 91 l Where reference numerals with the suffix b and 0 have been used to identify the same elements illustrated in FIGS. 1-7. In this embodiment it will be appreciated that the modified cover :plate 25b is also of the flush mounting type and therefore only the cover plate 25b and a plug 21b have been illustrated. The cover plate 25b is provided with a pair of apertures 28b adapted to receive the raised portion of the two sockets formed on a duplex receptacle of the type illustrated at 12 in FIGS. 1 and 3.

In order to permitthe use of a standard receptacle plug 211; without necessitating formation of special grooves of the type illustrated at 41 in FIG. 3,, the cover plate 25b is formed with a pair of recesses or socket-like depressions 29b adjacent the openings 28b so that the plug 21b may be inserted entirely into either of the depressions 29b. In keeping with this modified form of the present invention,

. the means for selectively locking the plug 21b in its complementary socket 2%- includes a spring biased locking lever 30b which is substantially entirely enclosed by the cover plate 25b. As in the case of the previous embodiment, the locking lever 30b is substantially L-shaped and is pivoted about a pin 31b secured to the cover plate and. projecting inwardly therefrom. A helical spring 32b is provided to bias one end 33b of the lever through an opening 34b formed in the wall of the depression 2% so as to maintain the locking lever 30b in its locking position. The opposite end 35b of the locking lever projects outwardly through an opening 36b formed in the margin 26b of the cover plate. Movement of the lever 30b, of course, may be elfectuated by pressing inwardly the extending portion 35b and thereby causing the latching portion 33b to retreat from the socket 2%.

As best seen in FIGS. 9 and 10, the latching portion 33b of the lever 30b is disposed to engage the outer peripheral shoulder 210 of the plug 21b when the plug is completely inserted in the depression 2%. In this maner, the modified cover plate 25b is adapted to receive and lock the plug 21b in the recess 2% without necessitating the formation of. a special groove or complementary locking portion on the plug. The latching portion 33b of the lever 30b is, as in the previous embodiment, desirably formed with a sloping cam surface which is engageable with the plug 21b so as to swing the lever 30b away from the opening 34b as the plug is inserted.

From the foregoing it will be appreciated that the novel cover plate 25 with cooperating locking lever 30 provides a particularly simple yet effective unit for locking a plug 21 in its complementary socket 20. In addition, since the locking lever 30 is substantially entirely enclosed by the cover plate, the likelihood of unintentionally tripping the locking device and the likelihood of sustaining an injury from undesirable projections are substantially eliminated. It will also be :ap preciated that the cover plate 25 is adapted to conventional manufacturing techniques and yet provides an attractive cover for the outlet 110. Moreover, the locking lever 30 is simple to construct and operate and also provides an effective plug retaining means. Finally, the provision for securing the locking lever 30 in its locking position by inserting a wire 45 into the aperture 44 eliminates the unwarranted or unintentional withdrawal of a plug 21 from its socket 20.

I claim as my invention:

1. For use with an electrical outlet box mounting a receptacle having one or more sockets, the combination comprising, a cover plate formed with a respective aperture to receive each of said sockets and adapted to cover the remaining portions of said receptacle and the entrance of said outlet box, said cover being formed with a raised marginal portion defining a socket-like depression adjacent each of said apertures, a lock lever pivotally mounted on the underside of said cover plate, said lever defining a latch portion at one end an operating portion at the other end, said cover being further formed to define an opening in one wall segment of said socket-like depression so as to receive said latch portion and another opening in said marginal edge portion for receiving said operating portion of said lever, a plug adapted to be received in said socket and dimensioned to substantially fill said depression, said plug being formed with a peripheral shoulder thereon, and means for biasing said latch portion of said lock lever into said opening in said wall segment so as to cooperate with said shoulder and lock said plug in said socket.

2. For use with an electrical outlet box mounting a receptacle having 'at least one socket, the combination comprising, a cover plate formed with an aperture to receive said socket and adapted to cover the remaining portions of said receptacle and the entrance of said outlet box, said cover being formed with a raised marginal portion defining a socket-like depression adjacent said aperture, a lock lever pivotally mounted on a pin projecting inwardly from the underside of said cover plate, said lever being substantially L-shaped with one end defining a latch portion and the other end defining an operating portion, said cover being further formed to define an opening in one wall segment of said socket-like depression so as to receive said latch portion and another opening in said marginal edge portion for receiving said operating portion of said lock lever, said lock lever thereby being substantially entirely enclosed beneath said cover plate when said cover plate is secured to said outlet receptacle, a plug adapted to be received in said socket and dimensioned to substantially fill said depression, said plug being formed with at least one partially circumferential groove therein adjacent the entrance end thereof, and means for biasing said latch portion of said lock lever into said opening in said Wall segment so as to cooperate with said groove and lock said plug in said socket.

3. For use with an electrical outlet box mounting a receptacle having at least one socket, the combination comprising, a cover plate formed with an aperture to receive said socket and adapted to cover the remaining portions of said receptacle and the entrance of said outlet box, said cover being formed with a raised marginal portion defining a socket-like depression adjacent said aperture, a lock lever pivotally mounted on the underside of said cover plate, said latch portion being generally wedge shaped with an inwardly sloping outer surface, said cover being further formed to define an opening in one wall segment of said socket-like depression so as to receive said latch portion and another opening in said marginal edge portion for receiving said operating portion of said lever, a plug adapted to be received in said socket and dimensioned to substantially fill said depression, said plug being formed with a tapered forward portion and at least one partially circumferential groove therein adjacent the forward portion thereof, and means for biasing said latch portion of said lock lever through said opening whereby said tapered portion of said plug engages said wedge shaped latch portion when said plug is inserted in said socket and said latch portion cooperates with said groove when said plug is fully inserted in said socket to lock the plug in the socket.

4. For use with an electrical outlet box mounting a receptacle having a plurality of sockets, the combination comprising, a cover plate formed with apertures to receive said sockets and adapted to cover the remaining portions of said receptacle and the entrance of said outlet box, said cover being formed with a raised marginal portion defining a socket-like depression adjacent each of said apertures, a lock lever pivotally mounted on the underside of said cover plate adjacent each of said apertures,

each of said levers defining a latch port-ion at one end an operating portion at the other end, said cover being further formed to define an opening in one wall segment of each of said socket-like depressions so as to receive said latch portion and another opening in said marginal edge portion for receiving said operating portion of one of said levers, a plug adapted to be received in each of said sockets and dimensioned to substantially fill one of said depressions, said plug being formed with at least one partially circumferential groove therein adjacent the entrance end thereof, and means for biasing said latch portion of each of said lock levers into said opening in said wall segment so as to cooperate with said groove and lock said plug in said cooperating socket, said operating portion of said lock lever adapted to project outwardly through said opening in said marginal edge portion of said cover plate when said latch portion of said lock lever is engaged in said groove in said plug whereby inward movement of said operating portion results in outward movement of said latch portion of said lock lever so as to selectively unlock said plug from said socket.

5. For use with an electrical outlet box mounting a receptacle having duplex-type sockets, the combination comprising, a cover plate formed with apertures to receive said duplex sockets and adapted to cover the remaining portions of said receptacle and the entrance of said outlet box, said cover formed with a raised marginal portion defining a socket-like depress-ion adjacent each of said apertures, a lock lever pivotally mounted on the underside of said cover plate, said lever defining a latch portion at one end an operating portion at the other end, said cover being further formed to define an opening in one wall seg ment of said socket-like depression so as to receive said latch portion and another opening in said marginal edge portion for receiving said operating portion of said lever, a plug adapted to be received in said socket and dimensioned to substantially fill said depression, said plug being formed with at least one partially circumferential groove therein adjacent the entrance end thereof, and means for biasing said latch portion of said lock lever into said opening in said wall segment so as to cooperate with said groove and lock said plug in said socket, said operating portion of said lock lever adapted to project outwardly through said opening in said marginal edge portion of said cover plate when said latch portion of said lock lever is engaged in said groove in said plug whereby inward movement of said operating portion results in outward movement of said latch portion of said lock lever so as to selectively unlock said plug from said socket, said operating portion of said lock lever being further formed to define an opening therein, and means insertable through said opening in said operating portion whereby said lock lever is retained in locked position to prevent the removal of said plug from said socket prior to removal of said means from said opening.

6. For use With an electrical outlet box mounting a receptacle having a pair of sockets, the combination comprising, a cover plate formed with apertures to receive said sockets and adapted to cover the remaining portions of said receptacle at the entrance of said outlet box, said cover being generally rectangular in shape and formed with a raised marginal portion defining a pair of socketlike depressions merging into said apertures, a lock lever pivotally mounted on the underside of said cover plate for each of said sockets, said lock levers each being journalled on an inwardly projecting pin secured to said cover plate and disposed adjacent diagonal corners thereof, each of said lock levers being substantially L-shaped with one end defining a wedge shaped latch portion and the other end defining an operating portion, said cover being further formed to define an opening in respective wall segments of said socket-like depressions so as to receive said latch portions and other respective openings in said marginal edge portions for receiving said operating portions of said levers, a plug adapted to be received in either of said sockets and dimensioned to substantially fill said respective depressions, said plug being formed with a peripheral shoulder thereon, and means for biasing said latch portions of said lock levers into said respective open- 8. ings in said wall segments so as to cooperate with said shoulder when said plug is inserted into either of said sockets whereby said plug is retained in said socket.

References Cited by the Examiner UNITED STATES PATENTS 1,510,977 10/1924 Clark 33991 2,273,729 2/1942 Tornblom Q 339-122 X 2,595,949 5/1952 Karlsson 339-75 X FOREIGN PATENTS 580,821 9/ 1946 Great Britain.

BOBBY R. GAY, Primary Examiner.

5 W. D. MILLER, Examiner. 

1. FOR USE WITH AN ELECTRICAL OUTLET BOX MOUNTING A RECEPTACLE HAVING ONE OR MORE SOCKETS, THE COMBINATION COMPRISING, A COVER PLATE FORMED WITH A RESPECTIVE APERTURE TO RECEIVE EACH OF SAID SOCKETS AND ADAPTED TO COVER THE REMAINING PORTIONS OF SAID RECEPTACLE AND THE ENTRANCE OF SAID OUTLET BOX, SAID COVER BEING FORMED WITH A RAISED MARGINAL PORTION DEFINING A SOCKET-LIKE DEPRESSION ADJACENT EACH OF SAID APERTURES, A LOCKER LEVER PIVOTALLY MOUNTED ON THE UNDERSIDE OF SAID COVER PLATE, SAID LEVER DEFINING A LATCH PORTION AT ONE END AN OPERATING PORTION AT THE OTHER END, SAID COVER BEING FURTHER FORMED TO DEFINE AN OPENING 